Various devices (STBs, PCs, mobile phones and other mobile entertainment devices) are used nowadays to consume the audiovisual content transported through multiple distribution infrastructures (satellite, radio, cable and IP networks). Providing unified commercial offers for all these technological platforms represents a key element for the service providers willing to differentiate themselves from their concurrence.
The technical means to deploy such cost-effective unified services are focusing on reusing hardware/software components on client side (chipsets for audiovisual decoding/de-multiplexing, smartcards for descrambling and the like) and to transport the unique audiovisual streams through various distribution infrastructure. This feature is made possible by encapsulating the audiovisual streams through multiple transport protocols. Known protocols for audiovisual data transport are UDP (User Datagram Protocol), RTP (Real Time Protocol) and RTSP (Real Time Streaming Protocol) for IP networks, as well as MPEG-2 TS (Transport Stream) for satellite, radio and cable networks.
For example, a digital TV service using satellite infrastructure for broadcasting would use MPEG-2 TS as transport protocol. The same operator wants to provide an IPTV (Internet Protocol Television) service for receiving devices connected to an IP network. In this situation, the audiovisual streams will be encapsulated according to two transport protocols: MPEG-2 TS to guarantee the transmission till the IP head-end infrastructures, and RTP or UDP for streaming the content to the devices connected to an IP network.
To protect the content transmission, most of the transport protocols contain specifications relating to security mechanisms: SRTP (Secure RTP) and ISMACryp (Internet Streaming Media Alliance) provides specification for content protection over RTP; DVB-CA (Common Scrambling Algorithm) specifies security mechanisms for content transport over MPEG-2 TS according to the DVB standard; IP SEC (Security) addresses the security of IP transport protocol.
Any of the security mechanisms designed for a specific transport protocol may be used to protect the content transmission. However, using such a mechanism a specific transport protocol would allow the de-protection of audiovisual stream only by the devices compliant to the specific transport protocol. Regarding the example presented above, distributing securely audiovisual streams to an IP-featured device would require a protection on IP level that would prevent a MPEG-2 TS featured device to access such an audiovisual stream.
This disadvantage is major: a service provider is forced to choose at the head-end of the distribution infrastructure a protection system that would strongly limit the choice of hardware devices for the end-user.
In addition, once the protection system was chosen, it will be difficult to access to the clear audiovisual stream at the level of the distribution chain, to insert a mark identifying the distribution nodes, for example, or to simply modify the content of the audiovisual streams.
It could therefore be advantageous to provide a method and system for securing the transport according to a plurality of transport protocols of an audiovisual stream to a device supporting any of the transport protocols. The same protected audiovisual stream would then be able to be de-protected at any level of the transport protocols, and not only at one specific transport protocol (the one where the protection process is applied).
In that situation, such a method would allow protection and de-protection of an audiovisual stream independent of the hierarchy of the transport protocols used for encapsulating the audiovisual content.